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Age / Sex : /
Age / Sex : 23 / F
Chief complaint : Left ankle pain
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
* Send Application Answers to Ja-Young Choi, MD ([email protected])
Courtesy : Jae-Chan Shim, MD. Seoul Paik Hospital, Inje University
Diagnosis: aneurysmal bone cyst
Discussion
Findings :
1. Plain radiograph of the left foot shows a round and well-defined osteolytic lesion in head of the talus surrounded by thin sclerotic rim.
2. MRI:
1) T1WI: Homogeneous low signal intensity with small high signal intensity portion in dependent portion demonstrating fluid-fluid level
2) T2WI: Very high signal intensity with small slightly low signal intensity portion in dependent portion revealing fluid-fluid level
3) Gd T1WI with fat sat: Peripheral rim-like and internal septal enhancement
Differential Diagnosis : Simple bone cyst, Giant cell tumor
Diagnosis : Aneurysmal bone cyst of the talus
Discussion :
An aneurysmal cyst is a expansile lesion containing thin-walled, blood filled cystic cavities. It is generally regarded as non-neoplastic in nature, and trauma appears to be important in the pathogenesis of some aneurysmal bone cyst, with well-documented examples of this lesion developing subsequent to acute fracture or other injuries. It is also well documented that aneurysmal bone cyst may accompany a variety of benign process of the skeleton and, less frequently, some malignant tumors.
Aneurysmal bone cysts are usually observed in the first, second, or third decade of life. Approximately 80% of affected patients are younger than 20 years.
Aneurysmal bone cysts are most frequent in the long tubular bone and spine, which together account for approximately 60% to 70% of cases. The small bone in the feet and, less frequently, the hands are affected in approximately 10% to 14% of cases. Within the long tubular bones, aneurysmal bone cysts are seen almost exclusively at metaphysis. Diaphyseal involvement occurs in about 8% of the cases. Epiphyseal extension of a metaphyseal aneurysmal bone cyst is uncommon and is usually apparent after closure of the growth plate. Osteolysis and osseous expansion are the dominant radiographic abnormalities of aneurymal bone cyst.
MR : Imagings typically show a well-defined lesion, often with lobulated contours. Internal septa with multiple fluid-fluid levels may be seen, although adjacent loculi may have markedly different imaging characteristics. Expanded low signal intensity rim surrounding the lesion are seen. Fluid-fluid level may also seen in telangiectatic osteosarcoma, giant cell tumor, cystsic chondroblastoma, and tumoral calcinosis.
References :
Resnick. Bone and joint imaging, 3rd edi. Elservier Saunders. Resnick. Diagnosis of bone and joint disorders, 3rd edi. Elservier Saunders.
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